Summary of Significant Accounting Policies (Details Textual) (USD $)	6 Months Ended		6 Months Ended	12 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 Maximum	Dec. 31, 2013 Maximum
Accounting Policies [Abstract]
Restricted cash	$ 4,900,000		$ 4,500,000
Short-term investment contractual maturities				2 years	2 years
Proceeds from sale/maturity of short-term investments	$ 109,138,000	$ 41,361,000

- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. For a classified balance sheet represents the current portion only (the noncurrent portion has a separate concept); there is a separate and distinct element for unclassified presentations.

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